Veterinary Surgery, 20, 4, 264-266, 1991

Excision of Oral Squamous Cell Carcinoma in a Horse JAMES A. ORSINI, DVM, Diplomate ACVS, DAVID M. NUNAMAKER, VMD, Diplomate ACVS, CARROLL J. JONES, DVM, and HELEN M. ACLAND, BvSC, Diplomate ACVP

A large oral squamous cell carcinoma in a 27-year-old Arabian stallion was removed by partial excision of the incisive bone. There was no gross evidence of recurrence or metastasis 5 months later.

27-YEAR-OLD ARABIAN stallion was referred to A the George D. Widener Hospital for Large Animals for treatment of a squamous cell carcinoma involving the rostral aspect of the hard palate of the incisive bone. Physical and laboratory examinations revealed no other abnormalities. The tumor was friable, expansive, had a fetid odor, and involved the incisor teeth with loss of the first right tooth. The diagnosis of squamous cell carcinoma was confirmed by incisional biopsy before referral. Radiographically, an osteolytic lesion was visible in the right rostral portion of the incisive bone, extending to the bone adjacent to the first left incisor, which had been displaced by the lesion. The first right incisor was missing; the second and third right incisors had lost normal alveolar bone and had also been displaced. On the intra-oral view, a soft tissue mass surrounded the incisors (Fig. 1). There were no radiographic signs of lung metastasis in standing lateral radiographs of the thorax.

Materials and Methods Xylazine* (200 mg) was administered intravenously. Anesthesia was induced with thiopental,? ketamineS and guaifenesin,§ and maintained with halothane" adminis-

tered via a nasotracheal tube in a semiclosed circle system. With the horse in dorsal recumbency, the gingival mucosa was incised at the level of the incisive bone from comer incisor to corner incisor. The submucosal tissue was elevated, exposing the most rostral portion of the incisive bone and creating a flap to cover the planned defect. The incisive bone was resected en bloc with an oscillating saw7 from corner incisor to corner incisor at the juncture between the incisive bone and maxilla rostral to the canine teeth. Right incisors 2 and 3 , and left incisors 1, 2, and 3 were removed. Hemorrhage was controlled with electrocautery, and absorbable gelatin sponge# and sterile gauze were packed into the nostrils. The gingival mucosa was advanced and sutured to the hard palate with vertical mattress sutures of size 0 polyglactin 9 lo.** A 6 X 4 X 6 cm mass was submitted for biopsy (Fig. 2). After recovery from general anesthesia, the horse was able to eat without difficulty, despite mild facial deformity. The frequency of feeding was gradually returned to normal after 24 hours; this included grazing 4 times a day, supplemented with a bran mash and sweet feed mix and three sections of hay 2 times a day. Histologically, neoplastic cells were arranged in variably-sized, oval to irregular solid islands, separated by thick and thin bands of vascularized connective tissue.

* Rompun. Mobay Corporation. Kenilworth. New Jersey. t Pentothal. Abbott Laboratories. King of Prussia, Pennsylvania.

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Ketaset. Fort Dodge Laboratories, Fort Dodge. Iowa. Q Glyceryl guaiacolate, Lee Laboratories, Inc.. Petersburg, Virginia. ' Fluothanr. Halocarbon Laboratories. Inc., Hackensack, New Jersey.

ll Slnthes, LTD, Wayne. Pennsylvania # Gelfoam, The Upjohn Company, Kalamazoo, Michigan ** Vicryl. Ethicon. Inc., Somerville, New Jersey ~~

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From the Section of Surgery (Orsini, Nunamaker) and the Laboratory of Large Animal Pathology (Jones, Acland), University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, Kennett Square, Pennsylvania. Reprint requests: James A. Orsini, DVM, University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, 382 West Street Road, Kennett Square, PA 19348.

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The neoplastic cells were moderately pleomorphic with large, oval, or round nuclei. with a moderate amount of stippled chromatin. They contained a large. often centrally placed nucleolus. and abundant eosinophilic cytoplasm. Intercellular bridges were prominent. Multifocal mild intraneoplastic necrosis and some keratinization were present. The mitotic rate was high. with up to seven mitotic figures per high-power field (Fig. 3). Groups of neoplastic cells invaded to the proximity of spicules of woven bone formed at the excised edge o f the incisive bone. Lymphatics and blood vessels were normal. There was surface hemorrhage and ulceration. Since the tumor margins were found to contain neoplastic cells, adjunctive radiotherapy (teletherapy) was recommended and performed to reduce the chance of local recurrence. The horse died 5 months later of ventricular arrhythmia while being anesthetized for radiotherapy. The report from the treating institution indicated no gross evidence of recurrence or local metastasis to regional lymph nodes.

Discussion

Fig. 1. Radiographs of an oral squamous cell carcinoma in a 27year-old Arabian stallion. (A) Lateral view. A soft tissue mass is visible adjacent to the destructive bone lesion (arrow). (B) Intra-oral dorsoventral view of the incisive bone. There is an osteolytic lesion The upper right first incisor is missing. The right second and third incisors have lost normal alveolar bone.

Squamous cell carcinoma. one of the most common neoplasms in horses, is an aggressive tumor characterized by extensive infiltration of surrounding bone and tissue. Despite its frequency of occurrence (about 7% occur in the oral cacity),' there are no reports of radical excision of this tumor from the oral cavity of horses, and reports of extensive surgery involving other oral tumors are rare.' Successful excision of oral tumors by mandibulectomy and maxillectomy has been reported in cats and dogs.".'-x The I-year survival rate after such excision 0 1 oral squamous cell carcinoma in 14 dogs was 934." In another report. also involving 14 dogs with squamous cell carcinomas, the median survival time after mandibulectomy was 15.8 months; elsewhere it was 9 months after surgical excision or radiation therapy.x Results of excision of squamous cell tumors ofthe feline maxilla or premaxilla have been relatively disappointing.' Wound dehiscence was the most frequently reported complication after maxillectomy and mandibulcctomy in dogs and cats.".8 Early dehiscence seemed to occur more often with simple interrupted sutures than with vertical mattress sutures. but the number of animals studied was too small to draw definite conclusions about the relationship ofdehiscence to suture pattern.' In the present casc. primaq wound healing followed closure with intempted mattress sutures ()fan absorbable synthetic braided material, polyglactin 910. Using a braided material in the oral ca\.*tYdid not result in suture sinus formation and wound dehiscence.

SQUAMOUS CELL CARCINOMA

The extent of a tumor at a given time is expressed as its clinical stage. In addition to making a histologic diagnosis. it is important to determine the clinical stage of the disease before making a decision about therapy. N o single staging system has been universally accepted to date. However, stage I usually indicates a neoplasm confined to its primary site of origin, stage 11 indicates metastasis to the regional lymph nodes, and stages 111 and IV indicate distant metastatic disease. This tumor fulfilled the requirements for a stage I neoplasm. Because the tumor margins contained neoplastic cells. radiotherapy was chosen for adjunctive treatment. We believe this to be the first report of partial incisive bone excision for an oral osteolytic tumor in the horse. Although no firm conclusions can be drawn from a single case, the fact that an early good outcome was obtained in spite Of the advanced age Of the and the size Of the tumor mass suggests that this procedure 'nay have

Fig 3 Photomicrograph of oral squamous cell carcinoma in a 27year-old Arabian stallion There are pleomorphic neoplastic cells (arrows) with a high mitotic rate (hematoxylin-eosin, magnification, X478)

value in the treatment of oral squamous cell carcinomas in horses. References I. Schuh JCL: Squamous cell carcinoma of the oral. pharyngeal and nasal mucosa in the horse. Vet Pathol 1986:13:205-207. 2. Junge RE, Sundberg JP. Lancaster WD: Papillomas and squamous cell carcinomas of horses. J Am Vet Med Assoc 1984:185:656-

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Fig. 2. Incisive bone resection. (A) Upper left, horse before positioning in dorsal recumbency; mass hidden by maxillary labium. Lower right, mass invading hard palate with planned line of incision and osteotomy (viewed with head in dorsal recumbency). (B) Gingival incision from left side. (C) Completed resection and closure of gingival and palatine tissue.

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Richardson DW. Fetter AW: Equine juvenile ing fibroma. Vet Pathol 1988:25:4 13-421. Enims SG. Harvey CE: Preliminary results of manillectomy in the dog and cat. J Small Anim Pract 19862739 1-306. Penwick RC. Nunamaker DM: Rostral mandibulectomy A treatment for oral neoplasia in the dog and cat. J Am Animal Hosp Assoc. 1987;23:19-25. Withrow SJ, Holmberg DL: Mandibulectomy in the treatment of oral cancer. J A m Anini Hosp Assoc 1983:19:273-286. Bradney IW, Hobson HP, Stromberg PC: Rostral mandibulectomy combined with intermandibular bone graft in treatment of oral neoplasia. J Am Anim Hosp Assoc 1987;23:61 1-615. Salisbury SK, L a m CC: Long-term results of partial mandibulectomy for treatment of oral tumors in 30 dogs. J Am Anini Hosp Assoc 1988:24:285-294. Ras W: Mandibulectomy and maxillectomy in the dog: Results of 75 cases. Scientific Meeting Abstracts-Amencan College of Veterinary Surgeons 1987:94: 105.

Excision of oral squamous cell carcinoma in a horse.

A large oral squamous cell carcinoma in a 27-year-old Arabian stallion was removed by partial excision of the incisive bone. There was no gross eviden...
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